This invention relates to an X-ray film cassette front plate used for a medical X-ray photographing device or the like. The term "front plate" as used herein is intended to means the front plate of an X-ray film cassette which is confronted with an X-ray source.
In general, an X-ray film cassette is made up of a front plate which is confronted with an X-ray source, a frame extending from the periphery of the front plate, and a rear plate coupled to the frame.
Heretofore, an aluminum plate or Bakelite plate is generally used to form an X-ray film cassette, because it is excellent in penetrability and uniform in material quality, and it can readily be transported being light in weight. On the other hand, instead of the X-ray film cassette, an X-ray film cassette of carbon-fiber-reinforced plastic (CFRP) has been proposed recently.
One example of the plate for the X-ray film cassette of CFRP comprises: a laminate of a carbon-fiber-reinforce plastic material with carbon fiber aligned and other X-ray penetrable materials; and carbon-fiber reinforced plastic layers formed on both surfaces of the laminate and those provided in such a manner that they are positioned symmetrical in a section of the laminate (cf. Japanese Utility Model Unexamined Publication No. 121467/1976). Another example of the plate is made up of an intermediate layer which is a carbon-fiber-reinforced resin layer, and aromatic polyamide fiber reinforced resin layers formed on both surfaces of the intermediate layer (cf. Japanese Utility Model Unexamined Publication No. 60255/1986).
The former is disadvantageous in the following points: Since the outermost layers are the CFRP layers, when the plate is cut to desired dimensions, the carbon fibers are finely split at the sections; that is, the resultant product is low in quality. It is rather difficult to completely remove the carbon fibers thus split. The plate is low in lightness or brightness because of its black surfaces. It is difficult to improve the lightness during molding by coloring the prepreg.
The latter is free from the fine splits of carbon fibers. However, the outermost layers, namely, the polyamide fiber reinforced resins layers are low in light-fastness, changes color with the lapse of time. Furthermore, it is rather difficult to cut the plate. That is, it must be cut with a special cutting edge such as a diamond head while being cooled with water or the like.